This is a proof-of-concept start at a Python version of Ruby's VCR library.
What it is supposed to do
Simplify testing by recording all HTTP interactions and saving them to "cassette" files, which are just yaml files. Then when you run your tests again, they all just hit the text files instead of the internet. This speeds up your tests and lets you work offline.
This should work with Python 2.6 and 2.7. It also seems to work with pypy. There aren't any context managers in 2.5 so I'm not bothering with that.
Currently I've only tested this (a little bit) with urllib2. It's known to NOT WORK with urllib.
How to use it
import vcr import urllib2 with vcr.use_cassette('fixtures/vcr_cassettes/synopsis.yaml'): response = urllib2.urlopen('http://www.iana.org/domains/example/').read() assert 'Example Domains' in response
Run this test once, and VCR.py will record the http request to
fixtures/vcr_cassettes/synopsis.yml. Run it again, and VCR.py will replay the
response from iana.org when the http request is made. This test is now fast (no
real HTTP requests are made anymore), deterministic (the test will continue to
pass, even if you are offline, or iana.org goes down for maintenance) and
accurate (the response will contain the same headers and body you get from a
Ruby VCR compatibility
I'm not trying to match the format of the YAML files. Cassettes generated by Ruby's VCR are not compatible with VCR.py. The API is similar but VCR.py doesn't have nearly as many features.
- Probably only works with urllib2.
- requests kinda works as long as you just do HTTP GETS and don't get too fancy.
- Loading a HTTPS url and then a HTTP url in the same cassette will cause the second load to use the data from the HTTPS version of the URL: Issue #3
- Loading urls that do a 301/302 redirect don't work: Issue #4
- I haven't tested PUT/DELETE requests
Similar libraries in Python
Neither of these really implement the API I want, but I have cribbed some code from them.
This library uses the MIT license